Container for transporting and storing hazardous substances and method for making the container

ABSTRACT

A container for transporting and storing hazardous materials such as Chlorine includes a cylindrical body having end caps. The end caps are welded to the body to form a pressure vessel. The end caps have a peripheral edge that is recessed with respect to the ends of the body to protect the weld against damage from impact. The configuration of the juxtaposed components forms a lap joint that can be affixed together by a fillet weld.

This patent application claims priority to U.S. provisional patent application Ser. No. 60/864,081, filed on Nov. 2, 2006.

TECHNICAL FIELD

The present invention pertains to transportation pressure vessels, and more particularly to containers for transporting and storing pressurized hazardous materials.

BACKGROUND OF THE INVENTION

Containers used to store toxic or hazardous chemicals are well known in the art. For many years manufacturers and users of various chemical substances have purchased containers to transport and store these substances. Some of the chemicals stored in these containers include chlorine, sulfur dioxide, as well as numerous other chemicals. It is appreciated that while these substances are useful for their intended purpose, in a certain state they may be hazardous if brought into contact with human beings.

One type of container for transporting hazardous substances is the multi-unit tank car. The containers may be sized and configured to store a particular amount of chemical for transportation. Typically the containers of this type are constructed from carbon steel. For safety purposes certain characteristics, such as wall thickness and material type, may be mandated by governmental regulations pertaining to containers for handling hazardous substances. In general, the containers are extremely durable and have a usable life cycle of many years or even decades. Durability is important in ensuring the longevity of storing these substances safely.

As more and more containers are manufactured and as the life cycle of these containers is relatively long, the need for containers of this type may diminish. Therefore, it is important to be able to compete cost effectively in the industry. What is needed is a container for storing hazardous substances and a method for constructing the containers that reduces costs while maintaining the standards to which these containers must be made.

BRIEF SUMMARY

In one embodiment the subject invention includes a method of constructing a welded pressure vessel that includes providing a generally cylindrical body having an end portion, the end portion having a peripheral lip, providing at least a first end member having a peripheral edge, the first end member having a convex configuration, i.e. convex to the pressure side of the vessel, positioning the peripheral edge of the first end member interior to the peripheral lip of the cylindrical body forming a lap joint, and, welding the peripheral edge of the first end member to the peripheral lip of the cylindrical body.

One aspect of the method of constructing a welded pressure vessel includes positioning the first end member such that the convex portion of the first member is facing interior to the generally cylindrical body.

Another aspect of the method of constructing a welded pressure vessel includes providing a generally cylindrical body having an end portion, the end portion having a peripheral lip and wherein the peripheral lip is angled inward to a centerline axis of the cylindrical body.

Still another aspect of the method of constructing a welded pressure vessel includes fillet welding the lap joint forming a weld on inner circumference of the chime between the cylindrical body and the end member.

Even another aspect of the method of constructing a welded pressure vessel includes providing a generally cylindrical body having an end portion, the end portion having a peripheral lip, wherein the body is constructed from 516 grade 70 carbon steel.

Yet another aspect of the method of constructing a welded pressure vessel includes providing a safety relief device, and, affixing the safety relief device to the at least a first end member.

In another embodiment of the present invention a freight container for transporting associated substances under pressure includes a generally tubular body having an interior surface and a centerline axis with first and second end members fixedly attached to distal ends of the body. At least a first valve for transferring associated substances into the freight container is included. The thickness of the body and the operating pressure of the freight container may be calculated by the equation:

${P = {\frac{\left( {2*S*t} \right)}{\left( {R - {0.4t}} \right)}\mspace{14mu} {where}}};$

P is the working pressure of the container;

S is the allowable stress of the container material;

R is the distance from the centerline axis to the interior surface; and,

t is the thickness of the tubular body.

In one aspect of the embodiments of the present invention the first and second end members are welded to the body and the minimum thickness of the body and the operating pressure of the freight container are related by the equation:

${P = {\frac{\left( {2*S*E*t} \right)}{\left( {R - {0.4t}} \right)}\mspace{14mu} {where}}};$

P is the working pressure of the container;

S is the allowable stress of the container material;

E is the efficiency of the weld joint;

R is the inside radius of the body; and,

t is the minimum thickness of the body.

In yet another aspect of the embodiments of the present invention the maximum working pressure is substantially 350 PSI, and more particularly equal to or less than 342 PSI.

In still another aspect of the embodiments of the present invention the minimum thickness of the shell is substantially 0.276 inches.

In another aspect of the embodiments of the present invention the body is constructed from ASME SA-516 Grade 70 carbon steel.

In even another aspect of the embodiments of the present invention the body is roll-formed into a generally cylindrical container having a longitudinal seam, where the longitudinal seam is fusion welded. Additionally, the first and second end members may be curved, where the orientation of the first and second end members is convex with respect to the operating pressure within the container and where the first and second end members are fusion welded to the body.

In yet another aspect of the embodiments of the present invention the first and second end members respectively form lap joints with distal ends of the body.

In another embodiment, the freight container for transporting associated hazardous substances under pressure may include a generally tubular body having first and second end members are welded to distal ends of the body and at least a first valve for adding fluid to the freight container under pressure where the minimum thickness of the body and the operating pressure of the freight container are related by the equation:

${P = {\frac{\left( {S*E*t} \right)}{\left( {R - {0.6t}} \right)}\mspace{14mu} {where}}};$

P is the working pressure of the container;

S is the allowable stress of the container material;

E is the efficiency of the weld joint;

R is the inside radius of the body; and,

t is the minimum thickness of the body.

In one aspect of the embodiments of the present invention the minimum thickness of the body and the operating pressure of the freight container may be related by a combination of a first equation:

$P = \frac{\left( {2*S*E*t} \right)}{\left( {R - {0.4t}} \right)}$

and at least a second equation,

${P = \frac{\left( {S*E*t} \right)}{\left( {R + {0.6t}} \right)}},$

where

P is the working pressure of the container;

S is the allowable stress of the container material;

E is the efficiency of the weld joint;

R is the inside radius of the body; and,

t is the minimum thickness of the body.

In another one aspect of the embodiments of the present invention the first and at least a second equation define a range of body thicknesses for a given operating pressure.

In yet another aspect of the embodiments of the present invention the thickness of the first and second end members may be calculated by:

P=((2*S*E*t ₁)/(M*L _(o))−t ₁(M−0.2))/1.67 where;

P is the working pressure of the container;

S is the allowable stress of the material;

E is the efficiency of the weld joint;

t₁ is the minimum thickness of the first and second end members;

M is a scalar factor; and,

L_(o) is the curvature radius of the first and second end members, where the curvature radius L_(o) is in the range of 27 inches to 33 inches.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of container for storing hazardous substances according to the embodiments of the invention.

FIG. 2 is a partial cutaway side view showing the components of the container for storing hazardous substances according to the embodiments of the invention.

FIG. 3 is a partial cutaway side view of the container for storing hazardous substances according to the embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings wherein the showings are for purposes of illustrating embodiments of the invention only and not for purposes of limiting the same, FIG. 1 shows a transportation and storage container depicted generally at 1. The container 1 may be constructed to contain one or more of a plurality of substances. In one embodiment, the substances may be hazardous substances or chemicals such as Chlorine, Sulfur Dioxide, Anhydrous Ammonia, or other hazardous materials. Typically, containers of this type have been constructed to contain 2000 pounds of Chlorine. As such, the phrase “Ton Containers” has been coined in referring to containers of this type. The container 1 may be fashioned as a generally cylindrical container as shown in the figures. In this manner, the body 3 of the storage container 1 may be curved around a central axis X and may have a circular cross section. The container 1 may also include end walls or end members 6. The end members 6 may be affixed to the body 3 such that the container 1 is capable of being pressurized while transporting and storing the hazardous substances. In one embodiment, the end members 6 may be welded to the body 3 as will be discussed further in a subsequent paragraph. Accordingly, the container 1 may also include one or more valves 15, which may be operational valves 15′. The valves 15 may be any type of valve as is appropriate for use with the storage of pressurized hazardous materials. The valves 15 may be used to fill and/or empty the container 1 of the contained substances as desired. Additionally other devices, which may be safety relief devices 17, may be utilized to provide pressure relief in the case of over-pressurization. Still, any manner of utilizing the valves 15 and/or safety relief devices 17 may be chosen as is appropriate for use with the embodiments of the subject invention.

With continued reference to FIG. 1, the body 3 or shell may be constructed from sheet steel roll-formed into the straight cylindrical configuration. In one embodiment, the body 3 or shell 3 may have a minimum thickness of 0.276 inches and may have a length in the nominal range of 80¾ inches and 89¼ inches long. It is contemplated in another embodiment that the range of container lengths may extend substantially from 50 inches to 125 inches. When roll-formed, the I.D., i.e. inner diameter, may be approximately 29¼ inches, although the inner diameter may be in the range of 25 to 35 inches. Additionally, the type of steel utilized in constructing the body 3 may be ASME SA-516 Grade 70 carbon steel. However, other grades of steel may be used that conform to the proper regulatory restrictions or exemptions including but not limited to Title 49 of the Code of Federal Regulations. The minimum thickness of the body 3 may be calculated based on the following equation:

P=(2*S*E*t)/(R _(s)−0.4t) where;

P is the working pressure of the container 1; S is the allowable stress of the material; E is the efficiency of the weld joint; R_(s) is the inside radius of the container 1; and, t is the minimum thickness of the shell. In one embodiment, the working pressure may be substantially 350 PSI. However, the working pressure may be chosen including but not limited to substantially 342 PSI or as is appropriate for use with the embodiments of the present invention. Given an inside diameter and allowing for the weld joint efficiency to be equal to 1, it will be readily seen that the thickness t can be calculated for one or more grades and/or type of shell material. Other embodiments may include similar equations such as but not limited to the following:

P=(S*E*t)/(R _(s)+0.6t).

It is to be construed that the equations, listed above, may be jointly considered when arriving at a minimum thickness for the shell 3 of the container 1.

The minimum thickness of the end member 6 may be calculated based on the following equation:

P=((2*S*E*t)/(M*L _(o))−t(M−0.2))/1.67 where;

P is the working pressure of the container 1; S is the allowable stress of the material; E is the efficiency of the weld joint; t is the minimum thickness of the end member after end member forming; M is a scalar factor that may be based at least in part on the inside crown radius L_(o) and knuckle radius r_(k) of the end member; and L_(o) is the crown radius. In one embodiment, the crown radius L_(o) may be substantially 29.9 inches. The crown radius may also be in the range of 27 inches to 33 inches. However, other radii for the crown may be chosen with sound engineering judgment. Other embodiments may include similar equations such as but not limited to the following:

P=B/(R _(o) /t) where;

B is a scalar factor; R_(o) is the outside radius of the end member 6; and, t is the minimum thickness of the end member after end member forming. Similarly, it is to be construed that the equations, listed above, may be jointly considered when arriving at a minimum thickness for the end member 6 of the container 1. Once the steel body 3 has been formed into a cylinder, the seam 7 may be fused together by welding to join the sides of the body 3. In one embodiment, the seam may be forge-welded. In another embodiment, the seam 7 may be fusion welded. More specifically, the welded joint may be a double welded butt joint. After the container 1 has been constructed post welding treatment, such as stress relieving, may also be performed.

With continued reference to FIG. 1 and now to FIG. 2, the end members 6, also termed head, may be constructed from the same type of material as that of the body 3, namely SA-516 Grade 70 carbon steel. However, the thickness of the end members 6 may be thicker than the body 3. In one embodiment, the thickness may be approximately 0.8125 inch nominal. A minimum thickness may be 0.6875 inch ( 11/16 inch). However, any thickness above the minimum thickness may be chosen with sound judgment as is appropriate for use with the embodiments of the subject invention. The end members 6 may be fashioned in the shape of a disk or plate having an outer diameter corresponding to the inner diameter of the body 3. This is necessary as the junction between the body 3 and the end members 6 will be fused to form the pressurized vessel, which will be discussed in detail below. The end members 6 may be curved at their respective center portions 9 thereby having a domed shape with a corresponding radius. When positioned in the body 3, the curved portion of the end members 6 may be convex with respect to pressure in the vessel 1. This may be utilized as a safety mechanism for relieving pressure in the container 1. In the case where pressure in the container 1 increases to a particular threshold, the center portion 9 of the end member 6 may invert, such that the center portion 9 becomes concave to pressure. It will be appreciated that the inverted end member 6 increases the overall volume of the container 1 thereby reducing pressure in the container 1. It is noted here that the container 1 may include two end members 6, each one disposed on distal ends of the body 3. Each end member 6 may be inserted convex to pressure or convex to the interior of the container 1. The end members 6 may also include a peripheral edge 8 extending substantially parallel with respect to a center line C of the end members 6. As the end members 6 are generally circular, the O.D., i.e. outer diameter, of the peripheral edge 8 may correspond to I.D. of the body 3. In one embodiment, the end members 6 may fit snuggly within the I.D. of the body 3 for welding the end members 6 in place.

With continued reference to FIGS. 1 and 2, the end member 6 may be placed inside body 3 such that the peripheral edge 8 is recessed with respect to the peripheral lip 4. In this way, the edge 8 and lip 4 may be juxtaposed to create a lap joint or fillet lap joint configuration. As mentioned above, the end members 6 may be welded to the body 3. In particular, the peripheral edge 8 may be welded to the peripheral lip 4 of the body 3. It is noted that the weld joint 11 is fashioned opposite the exterior surface of the body 3. That is to say that the weld joint is not exposed to external damage, as may occur from impact with another object. The components may be welded using a submerged arc procedure as is appropriate for use with carbon steel materials. However, the lap joint may also be welded using shielded gas welding or any other welding process as chosen with sound engineering judgment.

With continued reference to FIG. 2 and now to FIG. 3, after the structural components 3 and 6 of the container have been installed together, the ends 5 of the body may be tapered inwardly toward the central axis X in a process known as chiming to further protect the welded joint. The peripheral edge 8 may have a pre-chimed contour substantially parallel to the body 3. However, it is to be construed that the peripheral edge may have any configuration as is appropriate for use in constructing the container 1.

With continued reference to all of the FIGURES, a process of constructing a container 1 will now be discussed. The container 1 may be constructed by roll forming planar sheet steel into a straight cylindrical body having openings at distal ends of the body. The longitudinal joint of the cylindrical body may then be welded and subsequently stress relieved as necessary. First and second end members each having a convex configuration with respect to the interior of the body may then be inserted into the respective ends of the body. The end members may then be juxtaposed to the lip of the body such that peripheral edge of the end members and the lip form a fillet lap joint interior to the body cavity. The joint may then be welded sealing the interface of the components, i.e. end members and body, in a manner suitable for pressurization of the container. At any place in the process of constructing the container, holes may be bored in the components of the container and threaded for use in receiving valves, plugs or any other item suitable use in a container storing pressurized and hazardous material.

The invention has been described herein with reference to the preferred embodiment. Obviously, modifications and alterations will occur to others upon a reading and understanding of this specification. It is intended to include all such modifications and alternations in so far as they come within the scope of the appended claims or the equivalence thereof. 

1. A freight container for transporting associated substances under pressure, comprising: a generally tubular body having an interior surface and a centerline axis; first and second end members fixedly attached to distal ends of the body; at least a first valve for transferring associated substances into the freight container; and, wherein the thickness of the body and the operating pressure of the freight container are calculated by the equation: ${P = {\frac{\left( {2*S*t} \right)}{\left( {R - {0.4t}} \right)}\mspace{14mu} {where}}};$ P is the working pressure of the container; S is the allowable stress of the container material; R is the distance from the centerline axis to the interior surface; and, t is the thickness of the tubular body.
 2. The freight container as defined in claim 1, wherein the first and second end members are welded to the body, and, wherein the minimum thickness of the body and the operating pressure of the freight container are related by the equation: ${P = {\frac{\left( {2*S*E*t} \right)}{\left( {R - {0.4t}} \right)}\mspace{14mu} {where}}};$ P is the working pressure of the container; S is the allowable stress of the container material; E is the efficiency of the weld joint; R is the inside radius of the body; and, t is the minimum thickness of the body.
 3. The freight container as defined in claim 2, wherein the maximum working pressure is substantially 350 PSI.
 4. The freight container as defined in claim 2, wherein the maximum working pressure is substantially equal to or less than 342 PSI.
 5. The freight container as defined in claim 2, wherein the minimum thickness of the shell is substantially 0.276 inches.
 6. The freight container as defined in claim 2, wherein the body is constructed from ASME SA-516 Grade 70 carbon steel.
 7. The freight container as defined in claim 2, wherein the body is roll-formed into a generally cylindrical container having a longitudinal seam, and, wherein the longitudinal seam is fusion welded.
 8. The freight container as defined in claim 2, wherein the first and second end members are generally curved, and, wherein the orientation of the first and second end members is convex with respect to the operating pressure within the container.
 9. The freight container as defined in claim 8, wherein the first and second end members are fusion welded to the body.
 10. The freight container as defined in claim 9, wherein first and second end members respectively form lap joints with distal ends of the body.
 11. A freight container for transporting associated hazardous substances under pressure, comprising: a generally tubular body; first and second end members are welded to distal ends of the body; at least a first valve for adding fluid to the freight container under pressure; and, wherein the minimum thickness of the body and the operating pressure of the freight container are related by the equation: (S*E*t) ${P = {\frac{\;}{\left( {R + {0.6t}} \right)}\mspace{14mu} {where}}};$ P is the working pressure of the container; S is the allowable stress of the container material; E is the efficiency of the weld joint; R is the inside radius of the body; and, t is the minimum thickness of the body.
 12. The freight container as defined in claim 11, wherein the minimum thickness of the body and the operating pressure of the freight container are related by a combination of a first equation: $P = \frac{\left( {2*S*E*t} \right)}{\left( {R - {0.4t}} \right)}$ and at least a second equation, ${P = {\frac{\left( {S*E*t} \right)}{\left( {R + {0.6t}} \right)}\mspace{14mu} {where}}};$ P is the working pressure of the container; S is the allowable stress of the container material; E is the efficiency of the weld joint; R is the inside radius of the body; and, t is the minimum thickness of the body.
 13. The freight container as defined in claim 12, wherein the first and at least a second equation define a range of body thicknesses for a given operating pressure.
 14. The freight container as defined in claim 12, wherein the maximum working pressure is substantially equal to or less than 342 PSI.
 15. The freight container as defined in claim 12, wherein the minimum thickness of the shell is substantially 0.276 inches.
 16. The freight container as defined in claim 12, wherein the first and second end members are generally curved having a curvature radius; and, wherein the first and second end members are fusion welded to the body.
 17. The freight container as defined in claim 16, wherein the first and second end members are positioned inside the body at distal ends respectively forming lap joints.
 18. The freight container as defined in claim 16, wherein the first and second end members are convex with respect to the operating pressure of the freight container.
 19. The freight container as defined in claim 18, wherein the thickness of the first and second end members is calculated by: P=((2*S*E*t ₁)/(M*L _(o))−t ₁(M−0.2))/1.67 where; P is the working pressure of the container; S is the allowable stress of the material; E is the efficiency of the weld joint; t₁ is the minimum thickness of the first and second end members; M is a scalar factor; and, L_(o) is the curvature radius of the first and second end members.
 20. The freight container as defined in claim 19, wherein the curvature radius L_(o) is in the range of 27 inches to 33 inches. 